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1 1/2\" or 2 \" riser to thrid floor ?

Daniel_3 Member Posts: 543
I am finishing up the last touch up's on my one pipe steam system. Of course I saved the best for last. I have to install about 40 sqft. of radiation in the finished attic which was renovated and the previous installer (whom I won't bad mouth) installed an Arco thin tube of about 36 sqft. edr in a custom nook at the top of the stairs with about 30' of 1" inch pipe. Needless to say this radiator will not heat all the way across even with two varivalves and I am shying away from too much venting because of the issues with falling condensate which will by no means let the steam by in a nice dry form. I found good access at least to the second floor closet along the side of the chimney betwen the lath and chimney for the direct HW which gives ample room for 1 1/2" pipe with insulation up to that point. This will be about a 30' rise to get to a properly pitched horizontal runout so I'm wondering whether 2" maybe necessary on this end on the line run to the highest point. I have no porblem calculating the venting needed and will most likely install a Gorton #1 at the top of the drop before the radiator. As you all know this is not an easy task when saving lath and plaster walls and having to use the crawl space above the eaves. It's kind of daunting but then again I love this stuff.


  • Steamhead (in transit)
    For the vertical riser

    1-1/2" should be fine, you could even use 1-1/4" which has a capacity of 98 square feet. For the runout from the main to the riser, 1-1/4" is good for 55 square feet but I'd use 1-1/2" here, its 81 square foot capacity is closer to that of the riser. Horizontal pipes have less capacity than vertical ones unless they are dripped at the base of the riser.

    If the existing runout is 1", that might be your problem right there. It's only good for 28 square feet if not dripped. A 1-inch riser is good for 45 square feet, for what that's worth.

    A 1-inch radiator valve is rated 20 square feet, a 1-1/4" valve 55 square feet. I think a 1-1/2" runout and 1-1/4" riser and valve is the way to go.

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  • Daniel_3
    Daniel_3 Member Posts: 543

    Thanks for the reply Frank. After studying where the 1" pipe was run I just find it too annoying to tear it out and run 1 1/2" since the sill plates were drilled for the od of the 1" and run almost touching black pvc sewer lines from an upper full bath with new romex. How come they didn't do their homework? I figure to install a small fancy Gurney block wall type rad of two sections to connect up to the 1" in the nook and move the Arco 15 section 6 column to the far side for the new riser. With at least R20 in the rafters after the new roof as well and being the highest floor I belive this set-up will do the job and if not I can always get a larger rad for the new riser.
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